There is an increasing usage of water soluble polymers and copolymers in wastewater treatment industries. These compounds have shown desirable utility For the purpose of dewatering sludge and clarifying contaminated water.
The efficacies of the polymers or copolymers used will vary depending upon the type of monomers chosen to form the polymer or copolymer, the molecular weight of the synthesized molecule and, in the case of a copolymer, the placement of the selected monomers on the backbone of the copolymer. It is the latter characteristic that is the focus of the present invention.
Polymers with long sequences of two monomers can be categorized as block copolymers or graft copolymers. In graft copolymers sequences of one monomer are "grafted" onto a "backbone" of the second monomer type, ##STR3##
Graft copolymers have unique and highly desirable proper ties as compared to random copolymers or the blend of two homopolymers. Therefore, there is a great interest in preparing them. Few techniques described in the literature satisfy the need.
Furthermore, with ever increasing usages of water soluble polymers and copolymers in industries such as wastewater treatment, cooling, boiler and deposit control, coating, textile, mining, detergency, cosmetics, and papermaking, etc., there is an urgent need to synthesize novel water soluble graft copolymers for this broad range of applications.
More specifically, the use of recycled fibers is becoming an important aspect of papermaking for economic and environmental considerations The preliminary manufacturing steps in the use of recycled fibers for papermaking consists of repulping the paper sources, then removing the printing inks from the fibers. A typical deinking process utilizes a combination of chemical and mechanical techniques in several stages. Large amounts of water are used in the washing or flotation stages, wherein chemically treated ink particles and other contaminants are physically removed from the fibrous slurry. The wastewater, or effluent, from these stages is typically recycled back into the mill for reuse in the deinking process. As the recycled effluent contains dispersed inks, fiber fines and inorganic fillers, these contaminants must be removed to provide a clean water source for the deinking process and to prevent the dispersed inks from being reintroduced into the fibers. The effluent may also be discharged from the mill; thus, suspended solids must be removed from the wastewater to meet environmental regulations.
Clarification chemicals are typically utilized in con junction with mechanical clarifiers for the removal of solids from the effluent. Clarification generally refers to the removal of material by coagulation, and/or flocculation, then sedimentation or flotation. See the Betz Handbook of Industrial Water Conditioning 9th Edition, 1991, Betz Laboratories, Inc., Trevose, Pa. pages 23 through 30.
Conventional polyacrylamide copolymers have been used in this application. However, there still exists a need to provide a novel polymer in a more effective and economic treatment process. This objective is achieved by the present invention. The novel graft copolymers exhibit the desired efficacy for laser deink clarification applications.